This invention relates generally to variable resistance means and more specifically to a trimmable resistive network utilized primarily in conjunction with an integrated circuit.
In the fabrication and assembly of electronic components, many instances arise where the specific value of a required resistive element is not known until the fabrication and/or actual assembly of all the components are completed and various tests are conducted. An accurate determination of the value of resistance required quite often entails the physical substitution of resistive elements until the desired results are achieved.
In the integrated circuit (IC) technology, numerous techniques have been devised for providing resistors within the IC chip as fabricated, as well as for physically mounting chip resistors on the surface of the IC chip. These techniques have been relatively successful but in each instance the procedures for obtaining the proper value of resistance required for the particular application is most tedious and time consuming. In the case of fabricating resistors into an IC device during the fabrication process, it becomes near impossible to predict the proper value of resistance that will be required, as each separate element within the IC will be non-uniform from chip to chip, such that the value of resistance required for matching will vary greatly with each new fabrication. In regard to physically mounting chip resistors on the surface of the IC, for matching purposes, it becomes necessary to provide means for varying the resistance to achieve the proper matching. The present techniques employed for changing the value of the resistor for matching purposes consists of physically trimming the resistors or replacing the chip resistor with one of another size, or at the least, mounting additional series or parallel chip resistors to obtain the maching value desired.